Production of acetylene



Feb. 1, 1966 c. E. SHANNAHAN ETAL 3,

PRODUCTION OF ACETYLENE Filed March 5, 1962 V PREPURIFICATION PYROLYSIS,n ABSORBER GAS GAS TURBINE 5| PLANT 53 C02 ABSORBER AIR s4 sTEAM 1 Y"D972 -6l 49 WATER 2 ACETYLENE I ABSORBER WASTE HEAT BOILER ACETYLENESTRIPPER 39 36 ACETYLENE L, 34 WAU ACETYLENE WASH WATER AMMONIA WATERDISTILLATION INVENTORS 44 CORNELIUS E.SHANNAHAN HAYS c. MAYo BY @474 we.64 47 ,4. 0- M ATTORNEYS AGENT t include United States Patent 3,233,005PRODUCTION OF ACETYLENE Cornelius E. Shannahan, Garden City, and Hays C.Mayo, Huntington, N.Y., assignors to Pullman Incorporated, a corporationot Delaware Filed Mar. 5, 1962, Ser. No. 177,353 3 Claims. (Cl. 260-679)This invention relates to the recovery of acetylene produced by thepyrolysis of hydrocarbons. More specifical- 1y, it relates toimprovements in such a recovery process by which energy requirements ofthe process are supplied efficiently from the process itself.

A principal commercial process for the preparation of acetylene involvesthe pyrolysis of low boiling hydrocarbon feed stocks, i.e., lighthydrocarbons ranging from normally gaseous hydrocarbons through lightnaphthas. In the pyrolysis process, the hydrocarbon feed is maintainedunder closely controlled conditions of temperature, pressure andreaction time to provide a gas mixture containing a recoverable quantityof acetylene. As indicated, the process is applicable to the conversionor normally gaseous hydrocarbons as Well as normally liquidhydrocarbons. In the conversion of normally gaseous hydrocarbons thefeed material is preheated and combined with a quantity of oxygen in anamount sutficient to oxidize a portion of the hydrocarbon feed. Thisoxidation reaction supplies the bulk of the heat necessary for theconversion of the hydrocarbons to desired products. For the conversionof normally liquid hydrocarbons to acetylene, a suitable combustion gas,such as hydrogen or mixtures of hydrogen with carbon oxides, andhydrocarbon is burned with oxygen under conditions conducive to completeoxidation of the combustion gas. The liquid hydrocarbon feed, preferablypreheated, is injected into the hot combustion gases. reheating of theliquid hydrocarbon feed should be kept substantially below reactiontemperatures in order to avoid premature reaction.

Pyrolytic conversion of hydrocarbons is an endothermic reaction and thedistribution, of the pyrolysis reaction products is determined to asignificant extent by the reaction temperature and the reaction time inaddition to the feed composition. Pressure also influences productdistribution. As a general rule, high temperatures combined with shortreaction times favor the production of acetylene whereas lowertemperatures and longer reaction times favor the production of ethylene.Conditions most favorable for the production of acetylene involvereaction temperatures between about 1500 C. and about 3000 C. with areaction time between about 0.001 and about 0.01 second. Unfortunately,conditions must favorable for the production of acetylene also tend tofavor the production of higher acetylenic compounds such as methylacetylene, vinyl acetylene, diacetylene, etc, various other C -Chydrocarbons, hydrogen, carbon monoxide and carbon dioxide. Thecommercial use of acetylene as a chemical intermediate as, for example,in the preparation of chlorinated ethylenes, acetic acid, vinylchloride, vinyl acetate, neoprene, chloroprene, and acrylonitrile,requires acetylene of extremely high purity, n eces sitatingsubstantially complete removal of all of the foregoing materials fromthe pyrolysis eflluent.

Several recovery processes are known for producing acetylene of thenecessary purity. Generally, these processes involve the use of one ormore solvents which are circulated in one or more absorption-strippingsystems. Some of the solvents which are most commonly used acetone,butyrolactone, dimethylformamide, methanol, liquid hydrocarbons andliquid ammonia. In one such recovery process which is preferred, thepyrolysis gas, after removal of carbon dioxide and water,

, 3,233,0s5 Patented Feb. 1, 1966 is contacted with heavy naphtha underconditions suitable to absorb hydrocarbons heavier than acetyleneincluding higher acetylenic compounds. The resulting prepurified gas isthen contacted with liquid anhydrous ammonia which selectively absorbsacetylene leaving a tail gas containing hydrogen, carbon monoxide andmethane. The rich liquid ammonia is stripped prior to recycle to driveoil a pure acetylene product.

Regardless of the particular recovery process which is used, it isnecessary first to compress the pyrolysis gas since it is ordinarilygenerated at substantially atmospheric pressure and at least asubstantial superatrnospheric pressure is necessary for operation of therecover process. In the case of many recovery processes, the higher thepressure used, the more efiicient is the separation. Unfortunately,however, the costs of compressing the pyrolysis gas are always great andbecome greater with higher pressure. Thus, it may be uneconomical insome cases to take advantage of the increased efficiency possible withhigh pressure. Even where the recovery process is operated at arelatively low superatmospheric pressure, there is strong incentive forreduc ing energy costs of the process in general and of compression inparticular.

Accordingly, one object of the present invention is to provide a methodfor recovering acetylene from a gas produced by the pyrolysis ofhydrocarbons characterized by improved efiiciency and economy. Anotherobject of the invention is to reduce compression costs associated withacetylene recovery processes. Still another object of the invention isto make ciiicient use of tail gases separated from pyrolysis gas inconjunction with the recovery of acetylene therefrom. Various otherobjects and advantages of the invention will be apparent from thefollowing detailed discussion and description.

In accordance with the improved method of the invention, a gas turbineis used to drive the pyrolysis gas compressor. At least a portion of thetail gas separated in conjunction with the recovery of acetylene fromthe pyrolysis gas is supplied to the gas turbine as fuel whereby atleast a substantial portion of the power requirement of the compressoris supplied from the tail gas of the recovery process. In a preferredmethod of operation, still further improvements in overall etiiciencyare obtained by recovering heat from the gas turbine exhaust andsupplying this heat at suitable points in the recovery process.

A standard gas turbine plant is used to drive the pyrolysis gascompressor. This plant includes an air compressor, a combustion chamberand a turbine. Atmospheric air is compressed in the air compressor ofthe gas turbine plant to a pressure of about 50 to about p.s.i.g. Thecompressed air flows to the combustion chamber of the gas turbine plantwhere it reacts with tail gas from the recovery process. The amount ofcompressed air used is about 400 to about 500 percent in excess of thatrequired for stoichiometric complete combustion of the tail gas. As aresult of the burning in the combustion chamber, average gastemperatures of about 1250 to about 1500 F. are obtained. The hot gasesof the combustion chamber of the plant at high pressure together withsecondary air to insure complete combustion are then expanded in theturbine of the plant generating shaft power which is transmittedmechanically to the pyrolysis gas compressor. Thus, the production ofuseful work by expension is used in the performance of work of pyrolysisgas compression. The exhaust gas from the turbine is at substantiallyatmospheric pressure and a temperature of about 700 F. to about 950 F.In accordance with the preferred method of operation, this exhaust gasis passed to a waste heat recovery boiler in which there are at leasttwo coils for recovering heat from the exhaust gas prior to itsdischarge to the stack. In the first coil, a process fluid is circulatedfrom a tower in the acetylene recovery process requiring reboiling heatat a temperature level above about 250 F. In the second coil in thewaste heat boiler, stream is generated at relatively low pressures foruse throughout the plant. The exhaust gas from the turbine gives up heatto the fluids flowing in the coils and then flows to the stack at atemperature of about 400 to about 500 F.

Any suitable compressor can be used for pressuring the pyrolysis gas.Generally, it is preferred to use centrifugal compressors for thispurpose. In order to avoid or minimize polymer formation and depositionfrom the hea sensitive unsaturated hydrocarbons in the pyrolysis gas,the compression is preferably done in several stages with interstagecooling such that the pyrolysis gas never absorbs sufficient heat ofcompression to raise its temperature above about 220 F. The number-ofstages of compression required to satisfy this limitation will dependupon the inlet temperature, the first-stage-suction andfinal-stage-discharge pressures of the compressor and the temperature ofavailable coolant. The final discharge pressure of the pyrolysis gascompressor is selected on the basis of the particular recovery processused. On this basis, the final discharge pressure of the pyrolysis gascompressor is generally about 60 to about 200 p.s.i.g., and preferablyabout 170 to about 185 p.s.i.g.

The tail gas used as fuel in the gas turbine plant is any one or more ofthe substantially acetylene-free streams separated in the course of therecovery process. Its specific composition will vary in accordance withthe particular recovery process used and the point or points in suchprocess at which the tail gas is separated. In every case, it willcontain a substantial proportion of hydrogen and carbon monoxide. Inmany cases, it will also contain methane and small amounts of carbondioxide and gaseous hydrocarbons heavier than methane. In the case ofthe preferred recovery process described involving heavy naphtha andliquid anhydrous ammonia absorbents, it is preferred to use the gaswhich passes through both absorption operations and which, after waterwashing for removal of vaporized ammonia, contains principally hydrogen,methane and carbon monoxide. In prior art processes, this tail gas hasbeen wasted by burning in a flare stack and an important advantage isobtained by using at least part of it in accordance with the inventionas fuel in the gas turbine plant. This tail gas is produced in suchamounts that even where a neighboring synthetic methanol plant can use agas of this composition as feed, there will generally remain sufficienttail gas for use as fuel in a gas turbine plant to provide the entirepower requirement of the pyrolysis gas compressor.

The tail gas which is fired in the combustion chamber of the gas turbineplant is supplied thereto at a pressure of about 130 to about 150p.s.i.g., i.e., a pressure which is about 80 to about 120 p.s.i. greaterthan the air pressure. This differential pressure is necessary forproper control of the operation of the gas turbine plant. It isparticularly advantageous to operate the acetylene recovery process at asufficiently elevated superatmospheric pressure such that the tail gasseparated in the course thereof can be used directly, i.e., withoutfurther compression to meet the pressure requirement stated above forthe gas turbine plant. Greatest efficiency is obtained where thepressure of the recovery process and accordingly, the discharge pressureof the pyrolysis gas compressor are sufliciently high to meet thepressure requirement for the tail gas without special compressionthereof, but not substantially higher than that pressure.

As mentioned, a large stoichiometric excess of oxygen is supplied to thecombustion chamber of the gas turbine plant. As a result, the exhaustgas from the turbine of the plant contains a substantial proportion ofuncombined oxygen, generally about 16 toabout 18 mol percent. En-

6],. hanced efficiency in the heat recovery from the exhaust gas isobtained by firing supplementary fuel in the waste heat boiler to beburned using the uncombined oxygen in the turbine exhaust. Wheresupplementary fuel is fired, it can be a tail gas from the acetylenerecovery process including another portion of the same tail gas passedto the combustion chamber of the gas turbine plant or it can be anextraneous fuel such as natural gas or fuel oil. The amount ofsupplementary fuel which is fired is influenced by the amount ofuncombined oxyge in the turbine exhaust gas and the amount and level ofheat which must be supplied in the waste heat boiler.

The heat content of the exhaust gas can be used in the waste heat boilersolely for generating steam if desired. This steam can be used directlyin the process, for example as a stripping gas, or indirectly in theprocess, for example in a heat exchanger to provide reboiling heat. Thistechnique has the advantage of permitting separate control of heatexchangers in reboiling service. However, where reboiling heat isrequired in the process at a temperature level above about 250 B, it isoften advantageous, especially where water supply is limited, to passthe process fluid to be reboiled into indirect heat exchange in thewaste heat boiler With the exhaust gas. It is found that this method ismuch more highly efficient thermally than one where steam is generatedin the waste heat boiler at a sufficiently high temperature and pressuresuch that the generated steam can be used in a separate heat exchangerto provide reboiling heat at a temperature level above about 250 F. Theeconomic advantages of this technique increase with an increase in thetemperature level of reboiling heat required.

For a better understanding of the invention, reference is bad to theaccompanying drawing in which there is shown, in diagrammatic form,suitable apparatus for carrying out a preferred embodiment of theinvention.

In the drawing, a pyrolysis gas is introduced in line 311 having thecomposition given in the table below. This pyrolysis gas is obtained bythe partial combustion of natural gas with oxygen. Prior to entering theprocess in line 11, it is contacted with water and with oil to removefree carbon or soot and any polymeric hydrocarbons which may be present.The pyrolysis gas is compressed in a compressor 3'12 from a pressure ofabout 1.0 p.s.i.g. at a temperature of about 93 F. to a pressure ofabout 170 p.s.i.g. and a temperature of about F. This compression isdone in a centrifugal machine and in six stages after each of which thegas is cooled to a temperature of about 100 F. in order to preventoverheating of the pyrolysis gas and attendant polymer depositionproblems. During compression, the maximum temperature of the pyrolysisgas is about 220 F. The six stages of compression and the intercoolingare not shown in detail in the drawing in the interest of simplicity.

The compressed pyrolysis gas in line 13 passes to a C0 removal systemshown generally by absorber 14 in which tie gas is contactedcountercurrently with a total of about 73,676 gallons per hour of diluteaqueous ammonia to re move C0 The dilute aqueous ammonia is circulatedin a standard absorption-stripping system (stripper not shown) beingintroduced to absorber 14 through line 16 and withdrawn through line1'7.

The pyrolysis gas recovered from CO absorber 14 in line I18 passes to asystem for the removal of hydrocarbons heavier than acetylene showngenerally as prepurification absorber 19 in which the gas iscountercurrently contacted With a total of about 16,153 barrels perstream day (b.p.s.d.) of heavy naphtha. Prior to its introduction intoabsorber 19, the gas in line 10 is contacted with dilute caustic foradditional CO removal and is dried and cooled to 10 F., by means notshown. The composition of the gas entering absorber 19 is given in thetable below. The heavy naphtha (boiling range of about 300 to about 450F.) is circulated in a standard absorption-stripping system (strippernot shown) entering absorber 19 through operation of absorber 19 at atemperature of about 8 F. and a pressure of about 154 p.s.i.g., theoverhead gas in line 23 is substantially free of higher acetyleniccompounds and of other hydrocarbons heavier than acetylene. Thecsomposition of this gas is given in the table below.

The prepuriiied gas in line 23, at about 7 F. and about 152.2 p.s.i.g.,is then contacted countercurrently in acetylene absorber 24 with about359 gallons per minute of liquid anhydrous ammonia. The lean liquidammonia is introduced into absorber 24 at about 33 F. through line 26and the rich liquid ammonia, containing substantially all of theacetylene from the pyrolysis gas in line 33, is withdrawn from absorber24 at about -42 F. and is passed through line 27 to acetylene stripper28.

Acetylene stripper 28 is maintained at top conditions of about 13 F.andabout 13 p.s.i.g. and bottom conditions of about 6 F. and about 21p.s.i.g. Vaporous ainrnonia is introduced into the bottom of acetylenestripper 28 through line 29 at the rate of about 29,850 pounds per hourand passes countercurrently upwardly driving off the absorbed acetyleneinto the overhead in line 31. The lean ammonia from the bottom ofstripper 28 is withdrawn through line 32 and is returned to acetyleneabsorber 24 through line 26, for reuse.

The vaporous acetylene-ammonia mixture in line 31, having thecomposition given in the table below, is passed to an acetylenewater-wash column 33 where it is countercurrently contacted with about188 gallons per minute of cold water introduced through line 34 toabsorb the ammonia. Substantially pure acetylene product is recoveredoverhead of acetylene water washer 33 in line 36 at about 87 F. andabout 9.0 p.s.i.g. This product is of suflieient purity for use as achemical intermediate, as earlier described.

Returning to acetylene absorber 24, the unabsorbed gases includingvaporized ammonia, of the composition given in the table, are withdrawntherefrom in line 37 at a temperature of about -33 F. and a pressure ofabout 147.3 p.s.i.g. They pass to a tail gas water-wash column 38 inwhich they are countercurrently contacted with about 110 gallons perminute of cold water introduced through line 39 to absorb ammonia.

The ammonia-water solutionsfrom the two water-wash columns 33 and 38 arewithdrawn in lines 41 and 42, respectively, combined in line 43 andpassed to an ammoniawater distillation column 44 in which they areresolved into an overhead ammonia fraction (about 33,872 pounds perhour) in line 46 and a bottoms Water fraction (about 148,233 pounds perhour) in line 47. These fractions are returned for reuse as absorbents.The ammonia-water distillation column 44 is operated at a pressure ofabout 298 p.s.i.g. and temperatures of about 117 F. at the top and about422 F. at the bottom.

Returning to tail gas water-Wash column 38, the substantiallyammonia-free tail gas of the composition given in the table is recoveredoverhead in line 48 at about 66 F. and about 142.4 p.s.i.g. The portionof this tail gas not required as fuel is delivered from the processthrough line 49. The balance, or about 558,000 standard cubic feet perhour, is passed through line 51 to a combustion chamber 52 of a gasturbine plant indicated generally at 53. It is to be noted that at theoperating pressures of the described recovery process the tail gasdiverted to turbine fuel in line 51 requires no booster compression.

tmospheric air is introduced into the gas turbine plant 53 through line54 at a rate of about 525,000 pounds per hour to about 605,000 poundsper hour and is compressed to a pressure of about 50 to about 70p.s.i.g. in the air compressor 56 of the plant. The compressed air inconduit 57 and the tail gas from line 51 are combined and react incombustion chamber 52 producing a gas in conduit 58 at a temperature ofabout 1250 to about 1450 F. and a pressure of about 50 to about 70p.s.i.g. This gas is expanded in the turbine 59 of the plant producingthe shaft power necessary to drive pyrolysis gas compressor 12 and aircompressor 56. The horsepower requirement of compressor 12 of 11,200 isthus supplied entirely during normal operation using only process tailgas as fuel. Although only a single pyrolysis gas compressor 12 and gasturbine plant 53 are shown, two or more can be used in parallel toprovide flexibility. In the present example, two parallel compressorsand turbines are actually used.

The exhaust gases from turbine 59 are recovered in conduit 61 at atemperature of about 905 to about 920 F. and a pressure of about 4inches of water. In the preferred embodiment illustrated, the exhaustgases, having the composition given in the table, are directed to awaste heat boiler 62 where their heat is recovered in reboilingammonia-water distillation column 44 and in generating 450 p.s.i.g.saturated steam.

The reboiling duty of ammonia-water distillation column 44 is large,namely about 58,000,000 B.t.u. per hour, and is supplied at the hightemperature of about 422 F. This high-level heat is provided by passingabout 700,000 pounds per hour of Water from the bottom of column 44through line 63 by means of pump 64 to coil 66 in waste heat boiler 62.The resulting vaporized bottoms liquid is admitted to column 44 throughline 67.

For purposes of generating steam in waste heat boiler 62, boiler feedwater is introduced through line 68, preheated in coil 69 and passedthrough line 71 to steam drum 72. Preheated water is withdrawn fromsteam drum 72 through line 73, vaporized in coil 74, and returned tosteam drum 72 through line 76. The net steam production of 35,000 poundsper hour is delivered through line 77 to points of use in the process.The total duty of coils 69 and 74 in producing this steam is millionB.t.u. per hour.

The heat content of the exhaust gas in conduit 61 is augmented in wasteheat boiler 62 by firing supplementary fuel through line 78. Provisionis made to fire fuel oil of a heating value of about 26 million B.t.u.per hour or fuel gas of a heating value of about 12 to about millionB.t.u. per hour This supplementary burning is highly efficient by reasonof the high temperature of the uncombined oxygen in the exhaust gassupplied from conduit 61. The temperature of the flue gas out the stackof waste heat boiler 62 is about 450 F.

TABLE Compositions of principal streams, pounds per hour ReferenceNumeral for 11 18 23 31 37 48 *61 Stream COMPONENT *Weight percent.

When the foregoing process isstarted up, process tail gas is notavailable as fuel in the gas turbine plant 53. Although any suitablestart-up procedure can be used, it is preferred to use a small steamturbine (not shown) to start compressor 12, the steam for which isgenerated in waste heat boiler 62 using extraneous hydrocarbon as fuel,for example some of the hydrocarbon which is to be pyrolyzed to produceacetylene. After brief operation in this fashion, sufiicient tail gas isa available in line 51 to operate gas turbine plant 53.

A comparison between operating costs of the gas turbine and of astandard steam turbine applied in the above-described process showsthat, in fuel consumption alone, the steam turbine system requiresapproximately one-third more fuel than the gas turbine system. Otheroperating costs necessary with the steam turbine system and not involvedin the gas turbine system render the latter still more economicallyadvantageous.

It will be understood that the drawing and specific description thereofinvolve only the principal items of equipment. Various standard itemssuch as pumps, heat exchangers, control valves and the like are notshown in the interest of simplicity. The need for such standard itemsand the points in the process where they are used will be readilyapparent to those skilled in the art from the foregoing.

It will also be understood that various changes in the operatingconditions and of the specific arrangement of steps described can bemade without departure from the scope of the invention. For example, itwill be noted that in the stripping of the rich naphtha absorbent inline 22 from prepurification absorber 19, a tail gas will be producedconstituted by the impurities absorbed from the pyrolysis gas inabsorber 19 and the stripping gas. Since this tail gas is at arelatively low pressure, it is preferably not used as fuel forcombustion chamber 52, although such use can be made of it in accordancewith the invention. his particular tail gas can advantageously be used,however, as part or all of the supplementary fuel fired in waste heatboiler 62 through line 78. The specific example given is thus not to beconstrued as limiting but as merely illustrative.

Regardless of the particular solvent or solvents used for the recoveryof acetylene, or of the particular operating conditions used with thesolvent system in the recovery process, a tail gas will be separated atone or more points and this tail gas can be used with efliciency as fuelin a gas turbine plant to drive the pyrolysis gas compressor inaccordance with the invention.

What is claimed is:

1. In a process for the production of acetylene in which a hydrocarbonis pyrolyzed to produce a pyrolysis gas containing acetylene, hydrogenand carbon monoxide, said pyrolysis gas is compressed to a pressure ofabout 60 to about 200 p.s.i.g., and acetylene and a tail gas containinghydrogen and carbon monoxide are separately recovered from saidcompressed pyrolysis gas, the improvement which comprises supplying airat a pressure of about 50 to about 70 p.s.i.g. to a combustion chamberof a gas turbine plant, supplying at least a portion of said tail gas ata pressure of about 130 to about 150 p.s.i.g. to said combustion chamberof said gas turbine plant, the proportions of thereactants supplied tosaid combustion chamber being sufficient to provide about 400 to about500 percent air in excess of that required for stoichiometric completecombustion of the tail gas, supplying flue gas at a temperature of about1250 to about 1500 F. and a pressure of about 50 to about 70 p.s.i.g.

from said combustion chamber :of-said'gas turbine plant to a turbine ofsaid gas turbine plant, expanding said flue gas with the production ofuseful Work in said turbine and supplying at least a portion of the workof said pyrolysis gas compressing step from that produced in theaforesaid expansion step.

2. In a process for the production of acetylene in which a hydrocarbonis pyrolyzed to produce a pyrolysis gas containing acetylene, higheracetylenic compounds, hydrogen and carbon monoxide, said pyrolysis gasis compressed to a pressure of about 170 to about 185 p.s.i.g., saidcompressed gas is contacted with heavy naphtha under conditions suitableto absorb higher acetylenic compounds and to produce a prepurified gascontaining acetylene, hydrogen and carbon monoxide, contacting saidprepurified gas with liqiud ammonia under conditions suitable to absorbacetylene selectively and to leave a tail gas containing vaporizedammonia, hydrogen and carbon monoxide, washing said tail gas with waterto absorb vaporized ammonia and to produce ammoniafree tail gas and anammonia-water solution, and subjecting said ammonia-water solution tofractionation in a fractionation zone, the improvement which comprisessupplying air at a pressure of about 50 to about p.s.i.g. to acombustion chamber of a gas turbine plant, supplying at least a portionof said ammonia-free tail gas recovered at a pressure of about to aboutp.s.i.g. to said combustion chamber of said gas turbine plant, theproportions of the reactants supplied to said combustion chamber beingsuflicient to provide about 400 to about 500 percent air in excess ofthat required for stoichiometric complete combustion of the tail gassupplied, supplying flue gas at a temperature of about 1250 to about1500 F. and a pressure of about 50 to about 70 p.s.i.g. from saidcombustion chamber of said gas turbine plant to a turbine of said gasturbine plant, expanding said flue gas with the production of usefulwork in said turbine, supplying at least a portion of the work of saidpyrolysis gas compressing step from that produced in the aforesaidexpansion step, recovering exhaust gas at substantially atmosphericpressure and at a temperature of about 700 to about 950 F. from saidturbine of said gas turbine plant and cooling said exhaust gas to atemperature of about 400 to about 500 F. by passing the same in indirectheat exchange with a boiling liquid at a temperature above about 250 F.

3. The improved process of claim 2 in which said boiling liquid is abottoms fraction of said fractionation zone whereby reboiling vapors forsaid fractionation zone are generated by heat recovery from said exhaustgas.

References Cited by the Examiner UNITED STATES PATENTS 2,449,096 9/1948Wheeler 208-162 2,758,979 8/1956 Guthrie 252-417 2,915,570 12/1959Busch-Petersen et al.

252-419 X 3,026,969 3/1962 Braconier et al. 260-679 X 3,095,293 6/1963Kuerston 260-679 X ALPHONSO D. SULLIVAN, Primary Examiner.

1. IN A PROCESS FOR THE PRODUCTION OF ACETYLENE IN WHICH A HYDROCARBONIS PYROLYZED TO PRODUCE A PYROLYSIS GAS CONTAINING ACETYLENE, HYDROGENAND CARBON MONOXIDE, SAID PYROLYSIS GAS IS COMPRESSED TO A PRESSURE OFABOUT 60 TO ABOUT 200 P.S.I.G., AND ACETYLENE AND A TAIL GAS CONTAININGHYDROGEN AND CARBON MONOXIDE ARE SEPARATELY RECOVERED FROM SAIDCOMPRESSED PYROLYSIS GAS, THE IMPROVEMENT WHICH COMPRISES SUPPLYING AIRAT A PRESSURE OF ABOUT 50 TO ABOUT 70 P.S.I.G. TO A COMBUSTION CHAMBEROF A GAS TURBINE PLANT, SUPPLYING AT LEAST A PORTION OF SAID TAIL GAS ATA PRESSURE OF ABOUT 130 TO ABOUT 150 P.S.I.G. TO SAID COMBUSTION CHAMBEROF SAID GAS TURBINE PLANT, THE PROPORTIONS OF THE REACTANTS SUPPLIED TOSAID COMBUSTION CHAMBER BEING SUFFICIENT TO PROVIDE ABOUT 400 TO ABOUT500 PERCENT AIR IN EXCESS OF THAT REQUIRED FOR STOICHIOMETRIC COMPLETECOMBUSTION OF THE TAIL GAS, SUP-